1. Field of the Invention
The invention relates to an optical element, more particularly to a light-directing device adapted for directing light emitted by a light source.
2. Description of the Related Art
Referring to FIG. 1, a conventional illuminating device 1 includes a light source 11, and a light-guiding plate 12 for guiding light emitted by the light source 11. The light-guiding plate 12 has a light-receiving surface 121 facing the light source 11, and an inclined surface 122. A portion of the light emitted by the light source 11 is reflected by the inclined surface 122 to exit the light-guiding plate 12 via a light-exit surface 123 by virtue of internal reflection. The remaining portion of the light exits the light-guiding plate 12 via the inclined surface 122.
While a reflector (not shown) can be placed at the inclined surface 122 in order to increase the rate of reflection occurred at the inclined surface 122 toward the light-exit surface 123, the overall optical efficiency of the conventional illuminating device 1 is still low.